An endpoint on your network
An IP phone is a device that places and receives calls over an IP network. A desk handset normally combines a microphone, speaker, keypad, display and network interface with calling software. A softphone performs a similar endpoint role on a computer or mobile device.
For a SIP desk phone, the PBX or provider supplies the calling account and routing. Plugging a phone into Ethernet can give it network connectivity without giving it an active extension. Provisioning supplies account settings and device policies, often through a managed configuration service.
A simplified logical view. A hosted service may combine PBX and carrier functions; actual signaling and media paths can differ.
Check the exact device, not the family name
A manufacturer family can contain models with different Ethernet speeds, wireless features, expansion options and firmware. A feature may be built in, require an adapter or be unsupported on a particular variant. Provider-specific firmware or enrollment locks can also affect reuse.
Before buying, verify the exact SKU, firmware track, supported provisioning method and service compatibility. For used equipment, confirm ownership release and administrative access before relying on a factory reset.
Plan power and placement
PoE can power a handset through a compatible Ethernet connection, but the switch must support the required standard and sufficient total budget. A network jack alone does not imply PoE. Some phones use a separate adapter that may not be included.
For a receptionist, test transfer, headset operation and busy-lamp keys in the intended PBX. For a warehouse worker, evaluate mobility, charging and coverage. Wi-Fi and DECT solve different access problems and should be assessed on site.
Prove the everyday workflow
A successful registration is the beginning of acceptance. Make calls in both directions, check hold and transfer, test voicemail indications and restart the device to confirm that provisioning persists. Document the recovery process before deploying many phones. The phone library separates purchasing guidance from model-specific evidence.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.